Separation device for separating grinding elements and ground suspension in an agitator mill

ABSTRACT

A separation device for separating grinding elements and ground suspension in an agitator mill having separation elements adjacent to the interior of the mill with alternatively vibrating and stationary separation elements and with gaps between said separation elements of a size to block passage of the grinding elements. The separation elements may be stacked or concentrically arranged in a plane and several vibrators may be used to vary the type of motion of the elements.

Bicik et al. Sept. 9, 1975 [54] SEPARATION DEVICE FOR SEPARATING 3.682399 8/1972 Kaspar ct al 241/172 x 3,814.334 6/1974 Funk 241/73 x GRINDING ELEMENTS AND GROUND SUSPENSION IN AN AGITATOR lVlILL Inventors: Vladislav Bicik, Birsfelden; Jan

Kaspar, Muttenz, both of Switzerland [73] Assignee: Gebruder Netzsch, Maschinenfabrik,

Selb, Germany [22] Filed: Sept. 30, 1974 [2l] Appl. No: 510,771

[30] Foreign Application Priority Data Sept. 28, I973 Switzerland 13981/73 [52] US. Cl 241/69; 24l/l7] [5!] Int. CI. B02C 17/18 [58] Field of Search 241/67, 69, 73, 74, I72, 241/l71, 175; 2lO/384, 385, 388

[56] References Cited UNITED STATES PATENTS 3.536.266 lO/l97U Kaspar ct al 24l/l72 Primary Examiner-Roy Lake Assistant Examiner-E. F. Desmond Attorney, Agent, or FirmKarl W. Flocks ments.

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SHEET 5 0F 55 SEPARATION DEVICE FOR SEPARATING GRINDING ELEMENTS AND GROUND SUSPENSION IN AN AGITATOR lVIILL BACKGROUND OF THE INVENTION The invention relates to a separation device for separating grinding elements and ground suspension in an agitator mill, and gaps, whose size blocks the passage of the grinding elements, being formed between the separation elements.

The invention relates above all to a separation device for a rapidly rotating agitator mill whose grinding container is charged with free grinding elements and, on a side, possesses a connection for the continuous feed of the material subjected to grinding, in which connection the separation device for separating the grinding elements from the processed ground material is arranged on another side of the grinding container.

There are already known various embodiments of separation devices. Generally one employs a screen or slitted-plate separation element whose holes or slits are smaller than the employed grinding elements. A separation element of this kind is indeed very simple in its structure; however, during its operation it exhibits the tendency of plugging up, e.g., by the grinding elements comminuted during the operation or the coarse ground material. During the processing of medium and highly viscous, non-Newtonian, pseudoplastic suspensions, a high drop of pressure exists at the partition and, accordingly, higher pressures prevail in the grinding container.

Another known separation device consists of a stationary ring and a rotating ring arranged on the agitator shaft. The gap, which is formed between the two rings and which is employed as a separation element, can be adjusted only with difficulty for smaller grinding elements and represents a relatively complex construction. The precision of adjustment of the gap is dependent upon the supporting arrangement and satisfactory rotation of the agitator shaft. In known embodiments, the free separation surface is limited by the maximum diameter of the rotating ring that can be used.

The material subjected to grinding represents almost always a nonNewtonian, pseudoplastic, thixotropic liquid, whose viscosity depends strongly on the shear gradient and the time of agitation. The ground suspension is rendered liquid in the grinding container through an intensive effect of agitation. On the other hand, in the vicinity of the separation device and especially on its surface, there may be formed zones wherein the suspension is not agitated and, consequently, it congeals. A relatively firm mass is formed in the mixture with the grinding elements, which mass adheres strongly to the separation device and exhibits a high resistance to the flow-through. Similar conditions may set in also in the interior of the separation device. Therein the suspension is not stirred and the velocity of flow possesses low values.

SUMMARY OF THE INVENTION The invention is based on the task of producing a separation device which avoids the above-mentioned disadvantages, i.e., provides the possibility of separating the ground suspension from the grinding elements with out an excessive resistance to flow even in the case of non-Newtonian, pseudoplastic, thixotropic liquids.

The problem is solved by proceeding from a separation device of the type described at the outset, according to the invention, in such a manner that the separation device possesses a vibrator, with which at least one separation element can be set into vibratory movement. Owing to such vibratory movement a high shear gradient is formed in the gap and additionally between the vibrating separation elements and the mixture of suspension and grinding elements in the interior of the agitator mill. This lowers the viscosity, so that the separation device as a whole possesses a low resistance to flow-through for the suspension and the gap or gaps do not exhibit the tendency of plugging up. The gaps may be very narrow, so that small grinding elements, e.g., having the diameter of 0.1 to 0.2 mm, may also be reliably separated.

A separation element that can be set into vibratory movement is arranged with advantage in each case between two stationary separation elements. This forms a plurality of gaps for the high flow-through of the suspension, the totality of such gaps resulting in an increased passage cross-section and a lower resistance to flow-through.

An embodiment provides a plurality of vibrators with which every separation element can be set into vibratory movement. The separation elements arranged side-by-side preferably exhibit differential frequency of vibration and/or direction of vibration and/or amplitude of vibration. The amplitude is situated with advantage between 0.1 and 5 mm, the frequency between 50 and 20,000 hertz. The two are selected expediently in accordance with size and specific weight of the grinding elements as well as in accordance with the amount of the suspension flowing through and the viscosity of the suspension.

The separation elements are preferably flat and possess faces between which the gaps are formed.

In an embodiment of this kind, the separation elements comprise a stack of annular plates arranged one above another; the lowest annular plate, that projects to the greatest extent into the agitator mill, possesses a closed surface and the annular plates together with the fastening elements are attached in alternation to a rod connected to the vibrator and to a rigid frame portion of the separation device, which frame portion is attached on the agitator mill, in which connection the fastening elements arranged in the interior of the separation device possess passages in the axial direction of the stack.

In a further embodiment, the separation elements consist of plates arranged in a plane, their inner and outer peripheral surfaces defining the gaps.

In an embodiment, a plate consists of a perforate plate and further plates of suitable shape are arranged in the holes.

The separation elements may also consist of a set of concentric annular plates.

The entire arrangement of the plates with advantage possesses circular, oval or quadrangular shape.

Agitating attachments oriented toward the interior of the separation device are arranged with advantage on the vibrating separation elements. In this manner, there is obtained a reliable liquefaction of the suspension as well as the cleaning of the exposed interior of the separation device.

The separation device is arranged in the agitator mill expediently outside the agitation zone proper, which reduces the wear of the separation device.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained by Way of example and with further details in the following text by means of schematic drawings, wherein:

FIGS. 1 to 3 show various arrangements of a separa tion device on an agitator mill;

FIGS. 4 to 6 show sketches of cross-sections through various embodiments of the separation device;

FIG. 7 shows a plan view of the separation elements;

FIG. 8 shows a schematic cross-section along the line 88 of FIG. 7 through a further embodiment of a separation device;

FIG. 9 shows a plan view of separation elements;

FIG. 10 shows a schematic cross-section along the line 10-10 of FIG. 9 through another embodiment of the separation device;

FIG. 11 shows a schematic crosssection through a further embodiment of the separation device;

FIG. 12 shows a cross-section through a modified embodiment of a separation device;

FIG. 13 shows a horizontal section through the device of FIG. 12 along the line 13-13 of FIG. 12;

FIG. 14 shows a cross-section through an embodiment of the separation device, which is again modified; and

FIG. 15 shows a horizontal section through the separation device of FIG. 14 along the line l5l5 in FIG. 14.

In FIGS. 1 to 3, an agitator mill designated as a whole by numeral possesses a container 22, into which the material to be ground is filled through a filling connection 24. The material is ground, dispersed, homogenized or emulsified in the container. Microbial, organic or inorganic suspensions may be employed as material to be ground, An agitator 28, which can be driven in rotation, is mounted in container 22 by means ofa tight bearing 26, that is protected against contact with the ground material.

At the end turned away from filling connection 24, container 22 is provided with a further connection that ends in a flange 32, to which a base plate 34 of a separation device is attached, the separation device being designated as a whole by numeral 36. Separation device 36 possesses an outlet connection 38 for discharging the ground suspension.

In the embodiment of the agitator mill according to FIG. 1, container 22 is horizontal and separation device 36 is inserted perpendicularly. In the embodiment of FIG. 2, container 22 stands upright and separation device 36 is inserted into obliquely-arranged connection 30 and, finally, in the embodiment of FIG. 3, container 22 is likewise horizontal; however, connection 30, into which separation device 36 is inserted vertically, is here connected to container 22 by means of pipes, so that the ground material flows around and along separation device 36.

The embodiment of the separation device shown in FIG. 4 possesses three separation elements arranged one above another. The upper two separation elements consist of ring plates 40,42, while the lowermost consists of a closed plate 44 comprising an annular bulge. Plate 40 is attached directly to base plate 34; lower most plate 44 is connected to plate 40 by means of fastening elements, that are not illustrated and may be arranged inside or outside the separation device. Central plate 42 is attached to a rod 48 by means of connection elements 46, the rod extending through a flexible bellows 50 and being connected to a vibrator 52. Vibrator 52 is attached to base plate 34 by means of bracket 54. In place of bellows 50, there could also be employed either a stuffing box, a lip seal or a similar packing element. Fastening elements 46 situated within the separation device possess axial passages 47 for passing the separated suspension.

On starting the operation of vibrator 52 (which may contain, for example, an armature to which rod 48 is attached, and a coil, the armature performing an oscillating movement when the coil is subjected to the action of alternating current), rod 48 and, therewith, plate 42 are set into vibratory movement. Gaps 56 formed between the faces of annular plates 40, 42, 44 change their size in vibrating manner in this connection. In FIG. 4, the vibratory movement is linear in accordance with an arrow 58 and directed from top to bottom; however, one may also select a vibrator which transmits to plate 42 a horizontally oriented vibratory movement or a segment-of-circle-shaped vibratory movement. In place of the annular plates, the stationary, the vibrating or both types of plates may be square, rectangular or of other shape.

During the operation of the agitator mill, the comminuted ground material flows in the form of a suspension through vibrating gaps 56 and is discharged from the separation device through outlet connection 38. Since gaps 56 are smaller than the grinding elements used in the agitator mill, the grinding elements are retained and separated from the ground material. The vibratory movement of plate 42 brings about an automatic cleaning of gaps 56, so that a plugging-up is avoided. At the same time, the viscosity of the ground material is lowered, which produces a lesser loss of pressure in the separation device. Additional advantages of the described embodiment consist in its simple structure, its very long useful life, and the simple adjustability of the gap width, e.g., effected by placing disks between the fastenings of the stationary plates.

If a larger surface of separation or a larger crosssection of flow-through is required, the separation device may be constructed in accordance with FIG. 5. This differs from the embodiment of FIG. 4 merely in that a plurality of vibrating plates 42 is connected as separation elements to vibrator 52 by means of connection elements 46 and that a corresponding greater number of stationary plates 60 is provided. Vibrator S2 of this exemplified embodiment is turned by in relation to that of FIG. 4, rod 48 possesses a bend of 90, so that vibrating plates 42 perform a horizontal vibratory movement in accordance with the arrow at the top of FIG. 5.

In the exemplified embodiment of FIG. 6, a gap 56' is formed between annular plate 40 attached directly to a base plate 34' and a plate 64 arranged in a recess of annular plate 40 and having the corresponding shape. Plate 64 is connected to vibrator 52 by means of rod 48. Base plate 34 of this embodiment is shaped upward in the area above plate 64, so that above plate 64 the ground material, flowing in this embodiment through gap 56' formed between the external peripheral surface of plate 64 and inner peripheral surface of annular plate 40, flows out through outlet connection 38. The

embodiment of FIG. 6 can be adapted simply to larger quantities of flow-through by having a plate 66, which is attached to base plate 34', consist of aperforate plate. Plates 68, possessing a shape corresponding to the holes, vibrate in such a plate and are'connected by means of connection elements 46 jointly to rod 48 of vibrator 52 as shown in FIGS. 7 and 8. i

In a further embodiment of the separation device of FIGS. 9 and 10, the stationary separation elements consist of concentric rings 70, that are connected rigidly to one another by means of connection elements 46'. The vibrating separation elements, consisting of rings 72 that are likewise concentric, are arranged between rings 70 and connected to rod 48 of vibrator 52 by means of connection elements 46.

The separation device of FIG. 11 possesses two vibrating plates 74,76 with gap 56 being formed between the two. Plate 76 is connected to vibrator 52 by means of rod 48; plate 74 is connected to a further vibrator 52' through a mount 78, so that in regard to amplitude and frequency different vibratory movements may be imparted to two plates 74,76. Base plate 34' of this embodiment possesses a plurality of bellows 50 for the passage of rod 48 and mount 78, respectively. This embodiment is employed preferably for highly viscous sus pensions, e.g., printing inks.

The separation device shown in FIGS. 12 and 13 possesses an intermediate plate 80 and two external plates 84 and 86, joined by means of bolts 82. Six agitator elements 88 are formed on intermediate plate 80. Further, intermediate plate 80 is connected to a shaft 90, that is fixed radially and axially by means of two bearings 92. A sleeve 94, which is attached with ribs 95 to base plate 34, provides the possibility of a rotary movement of external plates 84,86, that are sealed with an elastic diaphragm 96 and rings 97 in relation to base plate 34. A vibrator 52, which is rigidly connected to outer plates 84,86 through a housing 98 and a sleeve 98' firmly attached to the latter, produces torsional vibrations with a frequency of 20 to 20,000 hertz and with a peripheral amplitude of 0.1 to mm. Vibrator 52, firmly attached to vibrator 52, produces torsional vibrations with a smaller frequency of 0.01 to 100 hertz and a large angular amplitude of 5 to 90. The two, torsional and/or segment-of-circle-shaped movements, produced by vibrators 52 and 52', are added to each other and the resulting movement is transmitted to intermediate plate 80 by shaft 90, that is sealed by means ofa packing box 99. An elastic connection element 100 between housing 98 and ribs 95 is employed for limiting the movement which is imparted by vibrator 52 to housing 98 and external plates 84 and 86.

The described separation device possesses the advantage that the gap formed therein betweeen rapidly vibrating plates 80,84,86 is cleaned additionally by the slow torsional movement of intermediate plate 80. Agitating attachments 88 and 89 effect an intensive stirring in the interior of the separation device and hydrody namic impulses in gaps 56, that guarantee an obstruction-free operation of the device.

The separation device illustrated in FIGS. 14 and I5 possesses an outer ring 102, an inner plate 103, and an intermediate ring 104 as separation elements. Ring 104 is connected to shaft 90 with three agitating rods 105. Outer ring 102 is provided with an annular attachment I06 and three connecting crosspieces or agitating attachments 107, to which inner plate I03 is attached.

Otherwise, the fastenings and the vibratory drive of this embodiment are the same as in the embodiment of FIGS. 12 and 13.

The latter two embodiments may also be operated with a single vibrator.

In every one of the described embodiments, the vibratory movement of the separation elements produces additionally an increased performance of the agitator mill. Rotating agitator 28 arranged in the mill (see FIGS. 1 to3) affects the primary impacting of the grinding elements, that move in the entire inner space of the agitator mill. Secondary impacts are produced by the vibration of the separating elements. The impacting between the moving grinding elements is intensified through such vibrations; the number of collisions between the grinding elements is increased, and the work of grinding is improved.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

What is claimed is:

1. A separation device for separating grinding elements and ground suspension in an agitator mill, comprising separation elements adjacent to the interior of the agitator mill having gaps between said separation elements of dimensions to block the passage of grinding elements between said separation elements, characterized in that the separation device includes at least one vibrator and at least one separation element connected to said vibrator which can be set into vibratory movement.

2. A separation device as in claim 1 further characterized by at least two stationary separation elements, said at least one separation element which can be set into vibratory movement being arranged in each case between said at least two stationary separation elements.

3. A separation device as in claim 1 further characterized by said separation elements being flat and pos sessing faces between which said gaps are formed.

4. A separation device as in claim 3, further characterized by said separation elements comprising annular plates arranged one above another in the form of a stack, the lowest of said plates extending to the greatest extent into the agitator mill and possessing a closed surface, a rod connected to said vibrator, fastening elements attached to said rod and to said annular plates which can be set into vibratory movement, a rigid frame part attached to the agitator mill, said annular plates attached in alternation to said fastening elements and to said rigid frame, said fastening devices arranged in the interior of the separation device and possessing passages therethrough in the axial direction of the stack.

5. A separation device as in claim 1, further characterized by a plurality of vibrators with which each of said at least one separation element can be set into vibration.

6. A separation device as in claim 5, characterized in that adjacent separation elements exhibit differential frequency of vibration.

7. A separation device as in claim 5 characterized in that adjacent separation elements exhibit differential direction of vibration.

l l. A separation device as in claim 9, further characterized by said separation elements comprising a set of concentric annular plates.

12. A separation device as in claim 9, further characterized by the vibratory movement imparted by said vibrator being rectilinear.

13. A separation device as in claim 1, further characterized by agitating attachments oriented toward the interior of the separation device and arranged on said vibrating separation elements. 

1. A separation device for separating grinding elements and ground suspension in an agitator mill, comprising separation elements adjacent to the interior of the agitator mill having gaps between said separation elements of dimensions to block the passage of grinding elements between said separation elements, characterized in that the separation device includes at least one vibrator and at least one separation element connected to said vibrator which can be set into vibratory movement.
 2. A separation device as in claim 1 further characterized by at least two stationary separation elements, said at least one separation element which can be set into vibratory movement being arranged in each case between said at least two stationary separation elements.
 3. A separation device as in claim 1 further characterized by said separation elements being flat and possessing faces between which said gaps are formed.
 4. A separation device as in claim 3, further characterized by said separation elements comprising annular plates arranged one above another in the form of a stack, the lowest of said plates extending to the greatest extent into the agitator mill and possessing a closed surface, a rod connected to said vibrator, fastening elements attached to said rod and to said annular plates which can be set into vibratory movement, a rigid frame part attached to the agitator mill, said annular plates attached in alternation to said fastening elements and to said rigid frame, said fastening devices arranged in the interior of the separation device and possessing passages therethrough in the axial direction of the stack.
 5. A separation device as in claim 1, further characterized by a plurality of vibrators with which each of said at least one separation element can be set into vibration.
 6. A separation device as in claim 5, characterized in that adjacent separation elements exhibit differential frequency of vibration.
 7. A separation device as in claim 5 characterized in that adjacent separation elements exhibit differential direction of vibration.
 8. A separation device as in claim 5, characterized in that adjacent separation elements exhibit differential amplitude of vibration.
 9. A separation device as in claim 1, further characterized by said separation elements comprising plates arranged in a plane with their inner and outer peripheral surfaces defining said gaps.
 10. A separation device as in claim 9, further characterized by at least one said plate comprising a perforate plate with further plates of corresponding shape arranged in the holes of said perforate plate.
 11. A separation device as in claim 9, further characterized by said separation elements comprising a set of concentric annular plates.
 12. A separation device as in claim 9, further characterized by the vibratory movement imparted by said vibrator being rectilinear.
 13. A separation device as in claim 1, further characterized by agitating attachments oriented toward the interior of the separation device and arranged on said vibrating separation elements. 